High speed weighing system using an automatically balanced electrical circuit to provide a digital indication



Dec.. 8, 1964 R. o. MUNlz ETAL. 3,160,811

HIGH SPEED wEIGHING SYSTEM USING AN AUTOMATICALLY BALANCED ELECTRICALCIRCUIT To PROVIDE A DIGITAL INDICATION Filed March 31, 1 960 2Sheets-Sheet l COMPARISONI IRCUIT RAMP r GENERATOR Ey W M. /dwy/ dZi-Zg.

8 1964 R. o. MUNIZ ETAL 3,160,811

HIGH SPEED wEIGHING SYSTEM USING AN AUTOMATICALLY BALANCED ELECTRICAL.CIRCUIT To PROVIDE A DIGITAL INDICATION Filed March 3l, 1960 2Sheets-Sheet 2 IVENToR 3 man 5 o@ ffy.

Roero OrZz' Laurence R, Cu Zmez4 ,By MW? M. 57am/*yf AAA u (El I V +mUnited States Patent lce lldll Patented Dec. 8, 1964 HlGH SPEEDfl/Eboli' NG SYSTEM USENG AN AUTMATECALLY BAlAlsltED CAL ClllCUil T@Phill/EDE A DEGETAL ENDICA'HN Roberto @rtlz lvl'uniz, liviayaguez,Puerto Rico, and Laurence lit. @uli/er, Melbourne, lilla., assignors, hynnesne assignments, to Fairbanks llflorse lne, New Yer-lr, Nfl'., acorporation ci' Delaware Filed Mar. 3l, wat?, No. ,lila 3 Claims. (Cl.Sli/twig?) This invention relates to weighing methods and apparatus andis particularly directed to novel high speed weigh ing methods andapparatus for providing a substantially instantaneous indication of theweight of articles passing rapidly across the scale platform.

lt is frequently necessary or desirable to determine the weight ofarticles in motion, such as railroad cars moving along a track, truckstraveling along a road, or articles being passed along an assembly lineor conveyor sytern. Moreover, the weighing operation is preferablyaccomplished without interrupting the movement of such articles.

Numerous types of weighing systems have been proposed heretofore foraccomplishing this purpose. However, none of the prior art systems havebeen entirely satisfactory. Many oi the prior art systems have requiredat least momentary interruption of the motion of the articles to beweighed. Gther prior art systems modulate the frequency of an electricsignal to vary the number of pulses counted during a given period inaccordance with a weight to be measured. However, such systems aresubject to possible error as a result of variation in the time intervalmeasuring means or instability of the ca.- rier frequency. Moreover, allof the prior art systems have been relatively slow and inaccurate ascompared to the system of the present invention.

These disadvantages of prior art electronic weighing systems areovercome with the present invention wherein a novel electronic weighingsystem is provided which is demodulated with respect to time 'whereasthe prior' art systems are primarily time modulated.

The advantages of the present invention are preferably attained byproviding a novel electronic weighing system comprising a rst voltagesource establishing a voltage which is functionally related to theweight of the article to be weighed, a reference voltage sourceestablishing a linearly increasing reference voltage, a constantfrequency oscillator, counting means for counting the cycles of theoscillator output, and means for starting said counting means when thereference voltage starts its rise and for stopping said counting meanswhen the reference voltage is equal to the voltage from said lrstvoltage source.

Accordingly, it is an object of the present invention to provide a novelelectronic weighing system.

Another object of the present invention is to provide a novel electronicweighing system which is demodulated with respect to time.

A. speciiic object of `the present invention is to provide a novelelectronic weighing system comprising a iirst voltage sourceestablishing a voltage corresponding to the weight of an article to beweighed, a rercrence voltage source establishing a linearly increasingreference voltage, a constant frequency oscillator, counting means forcounting the cycles of the oscillator output, and means for startingsaid counting means when said reference voltage starts to rise and forstopping said countinU means when said reference voltage is equal to thevoltage from said first voltage source.

Another specific object of the present invention is to provide a novelmethod of weighing articles, said method comprising the steps orestablishing a iirst voltage corn responding to the weight of an articleto be weighed, establishing a linearly increasing reference voltage,establishing a constant frequency electronic signal, and counting thenumber of cycles of Said signal occurring during the period required forsaid reference voltage to reach a value equal to that of said rstvoltage.

These and other objects and features of the present invention will beapparent from the following detailed description taken in connectionwith the figures of the accompanying drawings.

In the drawings:

FlG. l is a block diagram of a typical electronic weighing systemembodying the present invention; and

FlG. 2 is a diagrammatic representation of the circuit of the electronicweighing system of HG. l.

ln that form of the invention chosen for purposes of illustration in thedrawings, FIG. 1 shows a typical electronic weighing system embodyingthe present invention and having a sampling rate circuit 2 which servesto periodically trigger the weighing system to provide a compietelyautomatic system. The sampling rate circuit 2 passes triggering pulsesto a reset gate 4 which responds to each triggering pulse by sending apulse to a reset circuit o and, thereafter, sending a pulse to a rampgate circuit The reset circuit o is then energized to reset a pluralityof counting units l@ to their zero indication iu preparation for theweight indication which is to be supplied to the counting units lll.Meanwhile, the ramp gate circuit 3 passes one pulse to a ramp generatorl2 and passes a second pulse, at the same time, to a counter gatecircuit lli. Upon receipt of the pulse from the ramp gate circuit d, theramp generator 12 begins to deliver a linearly increasing voltage to asuitable comparison circuit lo. At the same time the ramp generator l?.is started, the counter gate le applies a pulse to open a Shaper gatecircuit 1S. The Shaper gate circuit lll receives a constant frequencysignal from a suitable source, such as oscillator 2li, and converts thisto a pulse-type signal having a constant repetition rate. The positiveportion of this pulse-type signal is passed to a suitable pulse amplier22 and is then applied to the counting units 10 to be counted while thenegative portion of the oscillator signal is fed back to the reset gated to assure synchronization of the system.

When an article to be weighed is placed on the weight platform, notshown, load cell 24 is provided to establish a voltage having a valuefunctionally related to the weight of the article to be weighed. Varioustypes of suitable load cells for accomplishing this are well known inthe scale art. The output of the load cell 24 is arnplilied by asuitable amplifier 26 and is then applied to the comparison circuit loto be compared with the rising voltage from ramp generator l2. Thecomparison circuit 16 may be of any conventional type which receives andcompares two input voltages and emits a pulse when the values of theinput voltage are equal.

To briey review the operation of the system, an article to be weighed isplaced on the weigh platform of the scale causing the load cell Z4 toestablish a voltage functionally related to the weight of the article.This voltage is amplified by ampliiier 26 and is applied to thecomparison circuit lo. When the sampling rate circuit 2 delivers astarting pulse to the reset gate 4, the reset gate 4 passes a pulse toramp gate S and energizes the reset circuit o to reset the countingunits l@ to their Zero indication. Ramp gate il causes the rampgenerator 12 to start delivering a linearly rising Voltage to thecomparison circuit lo and, simultaneously, passes a pulse to the countergate 14. Counter gate 14 then activates the Shaper gate lil whichreceives a constant frequency Signal from oscillator Ztl and converts itinto a pulse type signal having a constant repetition rate. The positiveportions of these sneden 5 pulses are passed to a suitable pulse amplier22 and are then counted by the counting units lil. Meanwhile, thenegative portions of the oscillator signal are fed back to the resetgate 4 to assure synchronization of the system. When the rising'voltagefrom ramp generator l2 reaches a value equal to that of the voltage fromthe load cell 24, the comparison circuit 16 delivers a pulse to thecounter gate ldlwhich then closes the Shaper gate 13. This stops the owof pulses to the counting units it?.

By selecting the proper amplified voltage output per unit weight on theload cell 24, together with the proper slope of the rising Voltage fromthe ramp generator l2 and the proper frequency of the signal from theoscillator 2t), it will be found that the number of pulses counted bythe counting units lll will be equal to the weight of the article beingweighed. For example, if the amplified output of load cell 2d is onevolt per hundred pounds of weight on the Weight platform, and thevoltage from the ramp generator l2 rises at a rate of one volt permillisecond, a signal from oscillator Ztl of one hundred kilocycles persecond will cause the counting units .tuto provide an indicationcorresponding to the Weight of the article being weighed. Thus, if aweight of 658 pounds is placed on the Weigh platform, the load cellZd'will produce a voltage which will be amplified to 6.58 volts. Thevoltage from ramp generator l2 will reach this voltage in 6.58milliseconds at which tin e the comparison circuit le will emit a pulseto stop the ilow of pulses to the counting units til. However, duringthe period in which the voltage from ramp generator 12 is rising, theoscillator 2@ passed 658 cycles to the Shaper gate i8 and these produced658 pulses which were delivered to the counting units lil. Consequently,when the pulse flow is stopped by the pulse from comi arison circuit 16,the counting units itl will register 658, which is equal to the weighton the weigh platform. Moreover, the weighing operation can be performedat a rate of a hundred times per second and the rate can be increased ashereinafter described.

The counting units llt) are preferably of the type which provide avisual indication of the number of counts received. However, if desired,the weighing system may,

either additionally or in the alternative,'provide a signalcorresponding to the weight of the article being weighed and this signalmay be recorded or employed to control suitable apparatus in any of thevarious manners well known in the art. Moreover, while the ramp.generator l2 has been described as delivering a linearly risingvoltage, it will be apparent that, when desired, a ramp generator couldbe employed which would initially deliver a voltage equal to the maximum'load of the system and may linearly decrease the voltage delivered toequal the voltage from the load cell. ln addition, the system has beendescribed as being triggered by periodic pulses from the sampling ratecircuit 2. However, it is obvious that, if desired, the sampling ratecircuiti could be supplemented with or supplanted by manual,electromechanical or other suitable means for triggering the system.

FIG. 2 illustrates a typical circuit diagram for the weighing system ofFIG. l and will now be described in considerable detail to more fullyillustrate the structure and advantages of the present invention. Titleboxes have been added to FlG. 2 to facilitate identification oi thevarious components -and to provide a convenient cross reference to theblock diagram of FIG. 1.

Sampling Rate Circuit The function of the sampling rate circuit 2 is toautomatically trigger the system to initiate the weighing operation andtogovern the number of times per second that the weighing operation isto be performed. v The sampling rate may be substantially any desired'speed. However, suflicient time must be allowed during each weighingcycle for the voltage from the ramp generator l2 to rise to the fullload value. Moreover, where the weighing system of the present inventionis employed with auxiliary equipment, such as a printer or other datarecording device, the time required for such auxiliary equipment toperform its function may have a limiting effect.

The actual sampling rate is determined by a relaxation oscillatorcomprising a neon tube 28 in combination with capacitor Ztl and asuitable one of the resistors E52v selected by means of switch 3d. Thecathode of the neon tube 28 is connected to the control grid 36 of athyratron 38 and is biased above ground potential by a suitable resistordil. The thyratron 33 serves to amplify and invert the polarity ofpulses produced by neon tube 28. Supply voltage from a suitable source,not shown, is applied to the sampling rate circuit through conductor i2and thyratron is biased to cut-ofi by a negative voltage applied to thescreen grid 44 from a suitable source, not shown, through conductor 46.

Originally, both neon tube and thyratrcn 38 are non-conducting. However,the supply voltage causes a charge to build up on capacitor Si) whichincreases the potential across neon tube When the ring voltage of neontube 28 is reached, the tube will conduct and current will ow throughtube 28 until capacitor 3G is discharged to a value equal to theextinguishing potential of tube 28. The iiow of current through neontube 28 causes a potential drop across resistor di). Hence, a potentialwill now appear at grid 36 of the thyratron 38, driving the grid 36positive and causing the thyratro-n 3S to conduct. When thyratron 38conducts, current will flow through resistor d8, thereby lowering thepotential at point Sti and delivering a negative pulse to the reset gate4 to initiate the Weighing operation. This negative pulse will continueas long as neon tube 218 is conducting. However, when tube 28 ceases toconduct, grid 36 of thyratron 38 will be returned to ground potentialcausing thyratron 33 to cease conducting. Each time that neon tube 28and thyratron 38 are fired, a negative pulse will be applied to initiatea new weighing cycle. Thus, the system will proceed to perform weighingoperations automatically at a repetition rate determined by the valuesof capacitor 30 `and the selected resistor 32. Should it be desired totrigger the Weiglr ing system manually or mechanically, switches 4"] and52 may be provided. Gpening switch 457 prevents automatic operation ofthe system. Therefore, switch 52 may be operated manually or may beactuated by a treadle or other suitable device and serves to applypositive potential to the grid 36 of thyratron 38 to cause the thyratron38 to conduct. The thyratron 38 will continue to conduct as long asswitch 52 is closed and will cease to conduct when switch 52 is opened.

Reset Gate The reset gate 4- receives the negative pulse from thesampling rate circuit 2 and performs two functions. First, it produces apositive pulse which is passed to reset circuit ti to reset the countingunits it? to zero in preparation for a new weight indication. Secondly,the reset gate 4 produces a negative pulse which is applied to ramp gate8 to start the actual weihing operation.

The circuit of the reset gate d is a catho-de coupled multivibratorcircuit employing tivo triodes 54 and S6 with the cathodes thereofconnected together, as seen at 58, and with the control grid oi triode54 couplet to the plate of triode 56, through capacitor et), and to thesupply Voltage source, not shown, through resistor 62 and conductorFeedback from triode Se to triode 54tis provided through the commoncathode resistance 6e. With this arrangement, triode 5d is normallyconducting. Consequently, current ows through triode Sd creating apotential drop across resistor' 64. This drives the control grid oftriode 56 negative and prevents tric-dc 56 from conducting. Moreover,with triode 54 nor- 5 mally conducting, point 66 is maintained at apotential less than that of the supply voltage, by reason of a suitableresistor 68.

As discussed above, the sampling rate circuit 2 initiates the weighingoperation by developing a negative pulse at point 50. Since the controlgrid of triode 5o is coupled to point Sil, through capacitor 7h, thisnegative pulse is applied to the control grid of triode fifi and servesto extinguish triode 54 and capacitor 6h starts to discharge. This cutsoli triode 54 which stops the iiow of current through triode andimmediately raises the potential of point d6 to that of thc supplyvoltage. The rise in potential at point d6 serves as a positive pulseand is supplied, through conductor 72, to the reset circuit 6 to resetthe counting units ttl to zero. Furthermore, the cessation of currentiiow through triode Sd lowers the potential drop across resistor and,consequently, removes the negative bias from the control grid oi triodeS6. This condition allows triode S6 to conduct while capacitor 6@discharges through resistor 62. When capacitor 60 is discharged, thecontrol grid of triode 5d will no longer be negatively charged. Hence,triode 54 will begin to conduct again while triode 556 will beextinguished. With triode f-i again conducting, the potential of pointwill again be lowered. This lowering of point 66 serves as a negativepulse to trigger the ramp gate tl to start the actual weighingoperation.

ln addition, since the weighing operation or the present inventioninvolves generating pulses at a fixed frequency and then coun-ting thenumber of pulses occurring while the voltage from the ramp generator 12is rising to a value equal to that of the voltage from the load cell 2d,it will be apparent that the counting units il@ must start counting atprecisely the same moment that the voltage from the ramp generator l2starts to rise. To assure the coincidence of these events, means areprovided for synchronizing the pulse supplied to the ramp gate S withthe lirst pulse passed by oscillator' 2t? to the Shaper gate lt; to beapplied to the counting units liti. As described above, thc ramp gate 8is triggered by the negative pulse created at point 66 of the reset gatei when triode Sti is cut olf and conduction is renewed through triode54. Thus, by providing means for driving triode Sd to cut oli at theinstant that oscillator 2L@ sends a signal to the Shaper gate i8 to beconverted to a pulse for counting by the counting units lil,synchronization will be accomplished in a brute force manner. To dothis, the control grid of 'triode 56 is coupled by conductor 715 to apoint between the Shaper gate l@ and oscillator Ztl. As discussed morefully hereinafter in the description of the oscillator 20, theoscillator applies `a negative signal to conductor 74 each time a signalis passed to shaper gate lid to be concerted to a pulse for counting bythe counting units l0, ln this way, if triode 56 oi the reset gate 1l isnot fully cut off at the time that Shaper gate lil passes -a pulse tothe counting units 1h, the negative signal applied by oscillator' Ztl toconductor 71twill drive triode 56 to complete cut oth rthis forces thereset gate d to deliver the nega-tive pulse to the ramp gate 8 to startthe rising voltage from ramp generator l2, in the manner describedabove, and, thereby, assures synchronous operation of the system.

Reset Circuit The purpose of the reset circuit 6 is to reset thecounting units l@ to zero at the start of each weighing operation beforethey begin to register new information.

The reset circuit 6 comprises a thyratron 5l having the plate thereofconnected to the counting units through conductor 53 and supplied withsupply voltage from a suitable source, not shown, through resistor Thecontrol and screen grids of thyratron 5l are connected to the reset gate4 through conductor 72 and resistors d'7 and 59. Moreover, the screengrid is provided with negative bias from a suitable source, not shown,through red sistor 6l while the cathode is maintained above groundpotential by a suitable resistor 635 and is connected to the countingunits l@ by conductor 65. Also, a capacitor 67 is connected between theplate of thyratron 51 and ground.

ln operation, thyratron 5l is normally non-conducting due to thenegative bias applied to the screen grid through resistor 6l. Under thiscondition, capacitor 67 is positively charged. Whcn the positive pulsefrom reset gate l is applied to the grid, thyratron 51 becomesconductive. This causes the potential at the plate of thyratron 51 tofall and this reduction in potential is applied through conductor 53 tothe counting units 10 to cause the counting units lltl to reset to zero.Meanwhile, fthe flow of current through thyratron 5l causes a potentialdrop across cathode resistor 63. This raises the potential at thecathode of thyratron 5l and the rise of potential is applied throughconductor to the counting units to clear the previous indication.

When the potential on conductor 53 begins to fall, capacitor 67 beginsto discharge and tends to maintain conductor 53 at the high potential.However, capacitor 67 must discharge and, consequently, the potential onconductor 53 falls until it reaches the extinction potential ofthyratron 5l. Thyratron 51 will then be cut ofi until a subsequent pulseis received from the reset gate 4.

Ramp Gate The function ot the ramp gate tl is to start the actualweighing operation and, after the voltage from the ramp generator 12 hasreached the full load value, to shut off the ramp generator l2.

The ramp gate circuit is a cathode coupled multivibrator circuitcomprising two triodes 76 and '7S having the cathodes thereof connectedtogether and grounded, as seen at till. The triodes 76 and 78 areprovided with supply voltage from a suitable source, not shown, throughconductors 82 and the control grid of triode 7S is negatively biasedthrough conductor 84 from a suitable source, not shown. The control gridof triode 76 is coupled to the plate of triode 78 through capacitor 86while capacitor dit and resistor 9@ are connected in parallel betweenthe plate of triode 76 and the control grid of triode 78. The controlgrid of triode 76 is normally maintained positive by the supply voltagesource, not shown, through resistor @2. Yillus, triode 76 is normallyconducting while triode 7d is normally non-conducting. However, thecontrol grid of triode 76 is also coupled to point 66 of the reset gate4 through capacitor 94. Thus, when the reset gate d develops a negativepulse at point 66, as described above, the control grid of triode 76 ofthe ramp gate ti will be driven negative and triode 76 will be cut oiland capacitor 86 will become charged. When triode '76 is cut ofi,current will low through resistor 9d to make the grid ot triode 7S gomore positive. Therefore, triode 73 will be allowed to conduct. The flowof current through triode 73 lowers the potential at point 96 and thisdrop in potential appears as a negative pulse on conductor 98. Conductor@3 applies the negative pulse to the counter gate lli which then opensShaper gate 18 to pass pulses to the counting units lll. Simultaneously,the nega-A tive pulse developed at point 96 is delivered to conductorlil@ which applies the pulse to ramp generator 12 to start the linearlyrising vol-tage for comparison with the voltage from the load cell 24.While this condition obtains, capacitor 6 is discharging throughresistor 92, When the capacitor 36 is suiciently discharged, the controlgrid of triode 76 will again become positive and triode 76 will resumeconducting. As soon as triode 76 obtains conduction, the potential dropacross resistor 9d will be reduced. Thus, the control grid of triode 73will be driven negative by the biasing voltage applied throughconductordei. Therefore, triode 78 will be cut oil". When this occurs,point 96 will return to the potential of the supply voltage. This stopsthe application of the negative pulse to conductors 9S and 1th? andshuts off the ramp generator 12.

It will beapparent that the maximum voltage obtainable by the rampfgenerator 12 will bedetermined by the slope of the voltage increase andby the 'time required for capacitor 86 -to discharge.v Accordingly, topermit adjustment of the maximum voltage output of the ramp generator12, the slope of the voltage increase may be maintained constant whilethe value of capacitor d6 is made variable. In the alternative, thevalue of capacitor 86 may be fixed and the maximum output or rampgenerator 12 may be adjusted by varying those components of the rampgenerator i12-which determine the slope of the voltage increase.Obviously, the maximum voltage obtainable by the ramp generator 12should be at least equal to the maximum voltage which will be deliveredby the load cell 24 under full load condition. Moreover, the repetitionrate of the sampling rate circuit 2 and, hence, the number of weighingoperations which can be performed during a given period, is limited bythe length of time required for the ramp generator 12 to reach the fullload voltage. Accordingly, by increasing the slope of the voltageincrease and reducing. the time required for discharging capacitor S6,lthe repetition rate of the system may be substantially any desiredfigure. Thus, weighing operationmay be performed several hundred timesper second well within the capabilities of the present invention.

Ramp Generator The function of the ramp generator 12 is to provide anoutput voltage whichcincreases.. linearly with respect to time. It is bymeasuring the time required for this linearly rising voltage to reach avalue equal to that of a constant voltage developed by the load cell 24or the like that the weight of an article on the weigh platform of thescale may be determined.

The `circuit of ramp lgenerator 12 includes two triodes 102 and 104.Triode 102 serves as a voltage generator while triode 104 acts as abootstrap integrator to assure linearity of the outputof the rampgenerator 12. The cathode of triode 162 is grounded and triode 102 isprovided with supplyvoltage from a suitablel source, not shown, throughconductorltto, diode 16S, conductor 11i?, potentiometer 112 and parallelresistors 1M. A capacitor 116 is connected between the plate of triode102 and ground. The control grid of triode 162 is energized throughconductor 10u and is normally conducting. In this condition, capacitor116 is shorted to ground and the ramp generator 12 has no output.However, when the ramp gate 8 applies a negative pulse to conductorMiti, as describedabovethe control grid of triode 102 is driven negativeand triode 162 becomes non-conducting. As a result, capacitor 116 beginsto charge toward the potential of the supply voltage. rThis increasingvoltage appears on conductor 118 and is applied to one input of thecomparison circuit 16. However, the capacitor 11: charges exponentially,rather than linearly. As noted previously, triode 1% serves as abootstrap integrator to provide the desired linearity. The control gridof triode 1M* is connected between the plate of triode 162 and capacitor116, as seen at 12d. In addition, the cathode of triode 1M is biasedabove ground potential by resistor 122 and is connected to conductor111i by conductor 124.

When triode 102 is conducting, the grid of triode 104 is negative andtriode 194 will be cut oi. However, when triode 102 cuts off, thecapacitor Will begin to accumulate charge. As capacitor 116 accumulatescharge, the charging current applied to capacitor 116 will be equal tothe supply voltage minus the charge on capacitor 116 divided by theresistance of potentiometer 112 and parallel resistors 114. However, ascapacitor 11u becomes charged, the grid of triode 104 will becomemorepositive and triode 104 will become increasingly conductive. Moreover,the current `through triode ludwill be passed through conductor 124 andwill be applied to conductor 11u as a feedti back current and will,thus, increase the charging current applied to capacitor 116. If thegain of triode 104 is unity, it will be found that the desired linearityis obtained. This gain can be approximated within satisfactory limits.For example, triode having gains of .95 are commonly available and suchtriodes provide a maximum deviation from the desired linearity of only.05%. This variation can be tolertcd. Hence, the ramp generator 12provides a linearly increasing. output voltage which is supplied throughconductor 11d to the comparison circuit As discussed above in thedescription of the ramp gate 3, the maximum voltage obtainable by theramp generator 12 is a function of the time required for capacitor 36 oframp gate t; to discharge and the slope of the voltage increase. it wasalso noted above, that the maximum voltage of the ram generator 12 couldbe adjusted by maintaining the voltage increase slope constant andvarying the capacitance of capacitor Se of the ramp gate 8. In thealternative, the maximum voltage obtained bythe ramp generator 12 may beadjusted by maintaining the capacitance of capacitor Se of the ramp gatett constant and varying the voltage increase slope. The voltage increaseslope is determined by the capacitance of capacitor 11d and theresistance of potentiometer 112 and paralleled resistors 115i togetherwith the value of the supply voltage. Thus, the slope of voltageincrease may conveniently be adjusted by varying either the capacitanceof .capacitor 11d or the resistance of potentiometer 112.

Diode 163 is merely a protective device and is designed to cut off ifthe ramp generator output voltage approaches the value of the supplyvoltage. Thisis merely to protect the circuit components fromoverloading and is not necessary for the operation of the system.

Counter Gate As discussed above, the Weighing operation of the presentinvention involves measuring the time required for the rising voltagefrom ramp generator 12 to reach a value equal to that of the constantvoltage from the load cell To provide a measurement of this time,counter gate 14 functions to receive a pulse from the ramp gate 8 toopen shaper gate 13 to start a flow of pulses at a constant repetitionrate to the counting units 1t?. Subsequently, upon receipt of a signalfrom comparison circuit 16 indicating coincidence between the values ofthe rising voltage from ramp generator 12 and the constant voltage fromload cell 2d, the counter gate 1d acts to halt the rlow of pulses to thecounting units 1i?.

It will be seen that the circuit of counter gate 14 is a cathode-coupledmultivibrator circuit comprising two triodes and 123 with the cathodesthereof connected together and biased above ground potential by commonresistor 139. The grid of triode 12S is connected to ground throughresistor 132 and is coupled to the output of comparison circuit 16through capacitor 134. Also, the plate of triode 12S is coupled to thegrid of triode 126 through paraliel capacitors. 136 and is connected toa suitable supply voltage source, not shown, through resistor 13S. Thepiate of triode 12d is also connected to the supply voltage source, notshown, through resistor 1d@ and is coupled to the input of shaper gate18 through the resistance-capacitance circuit 11i-2. In addition, thegrid of triode 126 is connected to the supply voltage source, not shown,through resistor lidand is connected to point 96 of the ramp gate i5through conductor 93.

At the start of the weighing operation, no signal is ap-v plied toeither conductor 92S or capacitor 134. Therefore, the grid of triode 126is positive and triode 126 is conducting. The flow of current throughtriode 126 establishes a potential drop across resistor 13d which makesthe cathode of triode 12S more positive than the grid thereof.Consequently, triode 128 is cut off. When the weighing operation isinitiated, ramp gate 8 applies a negative pulse to point to start theramp generator 12 sns/,reir

il bias of a its grid,will be cut olf. Therefore, the current iiowthrough triode 156 will cease to be pulsed and no additional pulses willbe applied to pulse amplier 22. Thus, no further counting will bel doneby counting units 10.

Pulse Amplifier The pulse amplifier 22 serves to receive positive pulsesfrom the Shaper gate 18-and to apply them as amplified negative 'pulsesto the counting unit l@ to cause the counting units to indicate thenumber of pulses received while thev voltage ramp generator 12 ywasrising to the value of the voltage from load cell 24 and, hence, toindicate the weight of the article on the weigh platform of the scale.

The circuit of pulse amplifier' is a paralel triode circuit having twotriodes 178 and 18d each having their cathodes, grids and plates coupledto the co esponding electrode of the other. The cathodes are groundedwhile the grids are biased above ground by resistor 182. Supply voltageis appliedfrorn a suitable source, not shown, through parallel resistors184. Moreover, the grids of triodes 178 and 188 are connected to theShaper gate 18 through conductor 1174 while the plates are coupled tocounting units through capacitor 186.

In operation, triodes 178 and 18d are both normally conducting. However,upon recepit of a positive pulse from Shaper gate 18 through conductor174, the grids are driven more positive, causing the tubes to conductmore heavily, as a result, the potential at point 188 is reduced andappears as a negative pulse across capacitor 186.- This negative pulseis received by the counting units 1li and is registered as a count Uponcessation of the positive pulse from Shaper gate 18, conduction throughtriodes 17S and 18@ returns to normal and the potential at point 188 israised pending receipt of a subsequent pulse to be counted.

The counting units 10, comparison circuit 1e, load cell 24 and load cellamplifier 26 are conventional items available commercially and are onlyof interest in the present invention in combination with the othercomponents of the system. It will be apparent that any similarcommercial items having suitable characteristics may be employed.

Moreover, while the system of the present invention has been describedas an electronic weighing system, it will be apparent that the systemmay be employed for measuring or indicating substantially anyinformation which can be presented by a constant voltage having a valuecorresponding to the information to be displayed. Thus, for example,load cell 24 could be replaced by a thermostat or pressure responsivedevice having an output voltage corresponding to the temperature orpressure to be measured.

ln addition, numerous other variations and modifications may obviouslybe made without departing from the invention. Accordingly, it should beclearly understood that the form of the invention described above andshown in the figures of the accompanying drawings is illustrative onlyand is not intended to limit the scope of the invention..

What is claimed is:

1. An electronic high speed weighing system comprisl ing a first voltagesource for establishing a voltage functionally related to the weight otan article to be weighed, voltage generating meansfor gene-rating alinearly increasing reference voltage, means for providing constantfrequency signals, a counting and indicating system including countingmeans connected to receive said constant frequency signals, countergating means connected to control the flow of said constant frequencysignals to said counting means, sampling means to provide a samplingpulse to initiate the operation of said weighing system, reset gatemeans having plural output terminals connected to said sampling means,said reset gate means operating upon the reception of a samplingpulseifrom said sampling means to providea first output pulse at one ofsaid plural output terminals, and subsequent thereto, a second outputpulse at another of said output terminals, a reset unit connectedtoreceive the iirst output pulse from said reset gate means, said resetun-it operating upon the reception of said first output pulse to providea signal to zero said counting means, ramp gate means connected toreceive said second output pulse from said reset gate means subsequentto the resetting of said counter means, said ramp gate means operatingto simultaneously provide a trigger pulse to said voltage generatingmeans and said counter gate means, said trigger pulse simultaneouslycausing said counter gate-means to open and permit the passage ofconstant frequency signals to said counter means and said voltage.generating means to generate a linearly increasing reference voltage,`and comparison means connected to receive and compare said linearlyincreasing reference voltage and said voltage from said first voltagesource, said comparison means directing a signal to close said countergate means when said reference voltage reaches a level equal to that ofthe voltage from said first voltage source.

2. The electronic high speed weighing system of claim 1 which includesmeans connecting said reset gate means to receive the constant frequencysignals'frorn said means for providing constant frequency signalswhereby said second output pulse from said reset gate means issynchronized with the iirst o such constant frequency signals receivedby said counter means.

3. The electronic high speed weighing system of claim 1 wherein saidreset gate means includes a cathode-coupled multivibrator circuit havinga rst normally conductive electronic valve means, second electronicvalve means coupled to said iirst electronic valve means to be renderedconductive upon the nonconduction of lsaid first electronic valve means,means connecting said rst electronic valve means to receive the samplingpulse from said sampling means, said sampling pulse rendering said iirstelectronic valve means nonconductive and said second electronic valvemeans conductive, whereby a tirst output pulse is provided at one ofsaid plural output terminals of said reset gate means, means connectedbetween said first and second electronic valve means to return saidsecond electronic valve means to the nonconductive condition subsequentto the reception of said sampling pulse whereby a second output pulse isprovided at a second output terminal of said reset gate means, and memsconnecting said reset gate means to receive the constant frequencysignals from said means for providing constant frequency signals,whereby said second output pulse from said reset gate means issynchronized with the first of such constant frequency signals receivedby said counter means.

References CJitcd by the Examiner UNITED STATES PATENTS 2,560,124 7/51Mofenson S40-347.1 2,717,994 9/55 Dickinson et al. 340-347 2,733,3581/56 Carapellotti S40-347.1 2,787,418 4/57 Maclnight et al. 340-3472,819,054 1/58 Thorsson 177-211 2,840,806 6/58 Bateman 340-347 2,870,436l/59 lnder 324-99 2,872,676 2/59 Dickinson 340-347 WALTER L. CARLSON,Primary Examiner.

ISAAC LlSANN, FREDERECK M. STRADER,

Examiners.

1. AN ELECTRONIC HIGH SPEED WEIGHING SYSTEM COMPRISING A FIRST VOLTAGESOURCE FOR ESTABLISHING A VOLTAGE FUNCTIONALLY RELATED TO THE WEIGHT OFAN ARTICLE TO BE WEIGHED, VOLTAGE GENERATING MEANS FOR GENERATING ALINEARLY INCREASING REFERENCE VOLTAGE, MEANS FOR PROVIDING CONSTANTFREQUENCY SIGNALS, A COUNTING AND INDICATING SYSTEM INCLUDING COUNTINGMEANS CONNECTED TO RECEIVE SAID CONSTANT FREQUENCY SIGNALS, COUNTERGATING MEANS CONNECTED TO CONTROL THE FLOW OF SAID CONSTANT FREQUENCYSIGNALS TO SAID COUNTING MEANS, SAMPLING MEANS TO PROVIDE A SAMPLINGPULSE TO INITIATE THE OPERATION OF SAID WEIGHING SYSTEM, RESET GATEMEANS HAVING PLURAL OUTPUT TERMINALS CONNECTED TO SAID SAMPLING MEANS,SAID RESET GATE MEANS OPERATING UPON THE RECEPTION OF A SAMPLING PULSEFROM SAID SAMPLING MEANS TO PROVIDE A FIRST OUTPUT PULSE AT ONE OF SAIDPLURAL OUTPUT TERMINALS, AND SUBSEQUENT THERETO, A SECOND OUTPUT PULSEAT ANOTHER OF SAID OUTPUT TERMINALS, A RESET UNIT CONNECTED TO RECEIVETHE FIRST OUTPUT PULSE FROM SAID RESET GATE MEANS, SAID RESET UNITOPERATING UPON THE RECEPTION OF SAID FIRST OUTPUT PULSE TO PROVIDE ASIGNAL TO ZERO SAID COUNTING MEANS, RAMP GATE MEANS CONNECTED TO RECEIVESAID SECOND OUTPUT PULSE FROM SAID RESET GATE MEANS SUBSEQUENT TO THERESETTING OF SAID COUNTER MEANS, SAID RAMP GATE MEANS OPERATING TOSIMUL-